DFO Flood Event 4434

USA, California, January-March, 2017

Flood Maps

Overview Map

Layers, bottom to top: Light reddish gray is all previous satellite-mapped flooding, 2000-present. Red is flooding mapped from ESA SAR and NASA optical data. Blue is pre-flood surface water. Flooding is only depicted when it extends beyond this "normal" water extent. Urban areas (satellite visible lights) are shown in gray.

The red areas are based on the automated NASA Global Flood NRT processor (see below) and a 14 day accumulation ending on the date shown. Also included is Sentinel SAR information from a March 20/January 19, 2017 comparison.


Geotif version

kmz (Google Earth) version


Event Reporting:

The Flood Observatory maintains a Global Active Archive of large flood events, 1985 to present. It is available to the public in both spreadsheet and GIS formats (both formats together provide the complete Archive). New events are entered into this archive each week. As of the end of 2016, there were 4432 events; each has a unique archive number.

Event Mapping:

In some cases, severe or damaging floods become the focus of Observatory inundation mapping. As part of collaborations with other organizations, and the Global Flood Partnership, the Observatory's maps and other data are made available to the public. With attribution, they can be used freely, including for commercial purposes, under the terms of the Creative Commons Attribution 3.0 Unported License. Geotif versions and GIS files are also provided for these maps through the links below. This event is selected for Observatory production of map and GIS data products.This web page and associated image and map (GIS) files are the permanent Flood Observatory record of this event.

This Event:

According to Flood List: "USA – More Record Rain in California, 1000s Evacuate Floods in San Jose (Updated) 22 FEBRUARY, 2017 BY RICHARD DAVIES IN NEWS, USA Update The mandatory evacuation area in San Jose has been expanded and now includes around 14,00 residents. In a statement earlier today, the City said: "Although the rain has largely stopped, flooding is continuing along Coyote Creek as reservoirs continue to spill and creek flow is extremely high. The area for mandatory evacuation has expanded and includes approximately 14,000 residents…" The area is along Coyote Creek, in the Coyote Creek 100 year flood zone plus approximately 250 feet, running from north of 280 to south of 101. Residents in the San Jose area should stay informed of events and can check regular updates here. Original Report, 10:20 CET, 22 February 2017 Hundreds of residents in San José were evacuated yesterday, 21 February, after levels of the Coyote Creek rose rapidly following further heavy rainfall in California. In Tuolumne County the heavy rain forced officials to open a spillway at the Don Pedro reservoir for the first time in 20 years. The latest series of downpours swept across northern California from Sunday 19 February to Tuesday 22 February. The National Weather Service (NWS) said the storm had weakened on Tuesday but further heavy storms are expected to hit Northern California this weekend. Venado in Sonoma County recorded more than 230 mm of rain in 72 hours. NWS said that daily rainfall records were broken in San Jose and San Francisco. Coyote Creek at Edenvale reached its highest ever level.".

For a web map service-based information, visit this DFO link and, zoom in to location of interest, and turn on appropriate data layers.

Suggested citation for this Creative Commons-licensed publication:

Brakenridge, G.R., and Kettner, A. J., date accessed, "DFO Flood Event #", Dartmouth Flood Observatory, University of Colorado, Boulder, Colorado, USA, http address.

Image Data Sources:

NASA Landsat 8 and ESA Sentinel SAR data if used in this map were obtained from the the U.S. Geological Survey Hazards Data Distribution System. and the Sentinels Science Data hub, respectively. Landsat 8 is jointly managed by NASA and the United States Geological Survey. Flood modeling results if used are from the NASA/University of Maryland Global Flood Monitoring System (GFMS), Drs. Robert Adler and Huan Wu, University of Maryland/ESSIC.

GIS Data Sources:

Event-specific water extent files supporting this Flood Event Map are located here. These may include high spatial resolution mapping such as from Sentinel or Landsat, or lower resolution files from MODIS. Draft versions may be posted and later revised; such revisions will include in the file names "r1", "r2", etc. The older files remain in this folder but generally should not be used. Both MapInfo and Shp formats are provided.

Notes on Sentinel SAR data processingj for this map: Two "exact repeat" images were retrieved from ESA's Sentinels Data hub, from before the flood (February 25, 2015) and during the flood (February 24, 2017). ESA SNAP software was used to reproject the two images intoa geographic (latitude and longitude) coordinate system. A 5x5 low pass filter was applied to both images. A threshold of 30 was applied to the flood image, resulting in a subset of only very dark (interpreted as water) pixels. A threshold of .3 was applied to a flood image/preflood image ratio product, resulting in a subset of pixels much darker in the flood image then before (this removes permanent surface water). A boolean "AND" step then provides only pixels that satisfy both conditions. GIS vectors (polygons) were then fit around pixels in this "flood water" result: red area on this map, and also provided as a shp file.

Click here for access to the automated daily MODIS-derived .shp file GIS record (record commences in 2011).

(Choose appropriate 10 deg x 10 deg map sheet directory and appropriate dates; longitude and latitudes refer to upper left map sheet corner; not all floods are mappable at the MODIS spatial resolution of 250 m)

Data from the Global Surface Water Explorer (a download data link is provided) is included as part the light reddish gray maximum previous water extent layer. It is based on Landsat data at a spatial resolution of 30 m (Jean-Francois Pekel, Andrew Cottam, Noel Gorelick, Alan S. Belward, High-resolution mapping of global surface water and its long-term changes. Nature 540, 418-422, 2016). On the map, it is shown beneath the NASA Shuttle Water Boundary Data (SWBD) surface water extent (90 m resolution), blue, processed from the 11-day February, 2000, SRTM mission and corrected using Landsat data.

When used, NASA NRT Global Flood Mapping maximum water extent for the years 2013-2015, at 250 m spatial resolution, provide part of the (light reddish gray) maximum flood mapped. DFO creates these annual water extent layers from data provided by that project, by accumulating into one annual file all of the daily .shp files for each year. DFO has also produced flood extent files through mapping of individual floods (~ yr 2000 to present); these are also included where available in this maximum flood extent layer.

Related Data:

Representative River Watch Flood Hydrograph (clickable dot above)

At selected locations, a time series of satellite microwave-based daily river discharge measurements are available from the Flood Observatory. See River Watch Global Display for more information. A sample from Site 88 is shown below.


Global Flood Monitoring System (GFMS) displays, if provided here, are from the University of Maryland.  Reference: Wu, H., R. F. Adler, Y. Tian, G. J. Huffman, H. Li, and J. Wang (2014), Real-time global flood estimation using satellite-based precipitation and a coupled land surface and routing model, Water Resour. Res., 50, doi:10.1002/2013WR014710. Global Flood Awareness System (GloFAS) displays, if provided, are from the European Commission Joint Research Centre and the European Centre for Medium-Range Weather Forecasts. Reference: Alfieri, L., Burek, P., Dutra, E., Krzeminski, B., Muraro, D., Thielen, J., and Pappenberger, F.: GloFAS – global ensemble streamflow forecasting and flood early warning, Hydrol. Earth Syst. Sci., 17, 1161-1175, doi:10.5194/hess-17-1161-2013, 2013.

Funding, Data and Institutional Support have been provided by:

NASA's Earth Sciences Program, the Latin American Development Bank, the World Bank, the European Commission (Global Disaster Alert and Coordination System, GDACS), the Google Earth Engine research awards program, the Committee on Earth Observation Satellites (CEOS) Disasters Working Group-Flood Pilot, the Japanese Space Agency, and the European Space Agency. GPM and AMSR-2 satellite microwave data for River Watch is processed first within GDACS. The Dartmouth Flood Observatory was founded in 1993 at Dartmouth College, Hanover, NH USA and moved to the University of Colorado, INSTAAR, CSDMS in 2010. The institutional support of both universities is gratefully acknowledged.

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